Lesson 1 ·Class 10 · Photosynthesis · Label Lab
Chlorophyll and the Chloroplast
Where the two reactions actually happen.
Tap any part of the diagram to learn its name and its job. Try: A single leaf cell holds about 40 to 50 chloroplasts, and a square millimetre of leaf surface can hold over 500,000 of them.
Free play — explore the diagram, or switch to "Label it yourself" and place every label. Switch to when you're ready to test yourself.
The chloroplast is divided into two working areas, and the division matters: the light reaction happens in the grana, where the chlorophyll is, and the dark reaction happens in the stroma around them.
What this lesson covers
What you do
- A single leaf cell holds about 40 to 50 chloroplasts, and a square millimetre of leaf surface can hold over 500,000 of them.
The parts you label
- Outer membrane — The outer of the two membranes enclosing the chloroplast.
- Inner membrane — The chloroplast is a double-membraned organelle, like the mitochondrion.
- Granum — A stack of thylakoid discs. The chlorophyll sits here, so this is where light is trapped.
- Thylakoid — One flattened disc within a granum. The light-dependent reaction takes place across its membrane.
- Stroma — The fluid filling the chloroplast around the grana. The light-independent (dark) reaction happens here.
- Stroma lamella — A flattened channel connecting one granum to another.
- Starch grain — Glucose made in photosynthesis is polymerised into starch and stored, which is what the iodine test detects.
Challenges to clear
- Tap where light is actually trapped.
- Tap where the dark reaction takes place.
- Label the whole chloroplast.
Hint
The chloroplast is divided into two working areas, and the division matters: the light reaction happens in the grana, where the chlorophyll is, and the dark reaction happens in the stroma around them.